Longitudinal studies have shown that continued exposure to the allergen after a patient has developed occupational asthma can lead to airway obstruction and hyperresponsiveness that persists for months or years after exposure ceases. There is good reason to think that continued exposure to allergens in the home or outdoors might have similar, adverse long term consequences. Techniques for quantitative air sampling, particle sizing, and immunochemical assay of amorphous allergens now exist. In previous grant periods we have refined air sampling strategies and equipment, as well as assay methods. We have measured aeroallergens in the work place in several occurrences of occupational allergy, in the outdoor air (Alternaria and moth) and in indoor air in dwellings. Unexpected results for outdoor aeroallergens were that both ragweed and oak pollen allergens occur in substantial amounts outside the pollenation period, and that even during flowering, up to half of the allergen is associated with particles smaller than pollen grains. We find allergen in other plant parts such as flowers, leaves and stems. Also, we find easily measurable quantities of moth allergen in the summer and fall. Indoors, we find not only house dust mite and cat but in Harlem tenements, substantial amounts of cockroach and mouse urinary protein. A newly built, tight, energy-efficient house had very much higher cat and mite allergen concentration in the air than older, conventional houses. In studies of high efficiency filters in this home, in Harlem tenements and in rat animal quarters, it appears that allergen production rate is more important than filtration in determining the allergen level in the air. We now propose studies with 5 aims: 1) to determine the relationship between ventilation and air permeation and the concentration of house dust mite and cat allergen in the air of approximately 1,000 dwelling in 5 cities; 2) to determine the effects of housekeeping activities on the concentration and particle size of mite and cat allergen in the home; 3) to determine whether outdoor insect aeroallergens cause asthma in patients with IgE antibody to insects in Portland, OR; 4) to determine whether the insect pollinated plants, dandelion and alfalfa, shed allergen into the air from other plants parts, as ragweed and oak do; and 5) to continue to refine and simplify the air sampling and assay procedures so they can become generally available to the practicing allergist.